1. Field of the Invention
The present invention relates to a signal lamp, and more particularly to a signal lamp structure that uses a light emitting diode as a light source.
2. Description of Prior Art
In general, a signal lamp is installed at an intersection of roads for directing pedestrians to walk or stop at a specific time, so as to assure the traffic flow and safety, maintain the order of traffics, and even lower the chance of traffic jams and accidents.
A common traffic signal lamp is the three-color traffic signal lamp that reminds pedestrians when to walk or stop by means of three colors: red, yellow and green. A traditional three-color signal lamp uses white bulbs to work with red, yellow and green lens or color bulbs that can emit red, yellow and green lights, and the signal lamp is covered and protected by a lampshade, so as to form a light emitting structure of the signal lamp. However, the traditional signal lamp structure that emits light by bulbs may be sheltered by sunlight in daytime easily or affected by rain in a rainy day, and thus weather conditions may directly affect a pedestrian's determination of the color of the signal lamp, and the chance for the occurrence of accidents may be increased.
To overcome the shortcomings of the traditional bulbs, a prior art uses a light emitting diode (LED) to substitute the traditional bulb as the light source of the signal lamp. Since the light source of light emitting diodes has the advantages of consuming less electric power and providing a high light emitting efficiency and a long life expectancy. As technology advances rapidly, the LED is much brighter than ever and thus the light source of light emitting diodes can be used for substituting the traditional bulb. Such arrangement not only saves power consumption and long time of use, but also provides high recognition in different weather conditions and greatly reduces pedestrians' misjudgment and the chance of occurrence of accidents.
In the present existing LED signal lamp structures, most light emitting structures require 125 to 188 pieces of light emitting diodes. Since the light emitting diodes will produce a considerable quantity of heat during their operations and general signal lamps usually do not come with a heat dissipating structure for the light emitting diodes, therefore a great deal of heat will be accumulated in the signal lamp structure. As a result, the temperature in the signal lamp will rise and may cause a short circuit of the light emitting diodes, and the signal lamp will become dimmer or inoperable, which will directly affect pedestrians' judgment and endanger traffic safety. Although a prior art structure uses an aluminum board for dissipating the heat produced by a plurality of light emitting diodes, the heat dissipating effect is very limited and unable to enhance the heat dissipation of the signal lamp, which becomes a blemish of the LED signal lamp structure.